1. Field of the Invention
This invention relates broadly to dental implants. More particularly, this invention relates to tools for the removal of maxillary bone for access to, dissection of and elevation of the subantral membrane of the maxillary sinus for osseous regeneration in order to increase the bony support structure for a dental implant, and for receiving a dental implant.
2. State of the Art
Dental implants have been used in dentistry for about twenty years. They offer a tremendous benefit to patients by allowing the replacement of missing teeth. The success of a dental implant is based on a variety of factors including: surgical technique, health of the patient, operator skill and, to a significant part, sufficient bone for the placement and integration of the dental implant. To that end, dental implants are commonly used in the anterior lower jaw, as this region provides sufficient bone quantity, quality and strength to support and hold the dental implant. However, the replacement of the maxillary teeth have presented a considerable challenge because after the loss of maxillary teeth the quality and quantity of the remaining supporting bone may be insufficient to properly and reliably support the dental implant.
More particularly, the maxillary complex is a three-dimensional bone structure composed of alveolar bone and basal bone. The maxillary teeth, and more specifically the teeth roots, are imbedded in the alveolar bone. The top of the maxillary complex forms the floor of the maxillary sinus and is covered by a thin diaphanous membrane known as the subantral or Schneiderian membrane (referred to herein as the “subantral membrane”). Once a tooth is removed from the maxillary complex, the surrounding alveolar bone is frequently resorbed because of the lack of physical stimulation and support of the teeth. This leads to a loss of bone mass and a corresponding reduction in the effective height and thickness of the bone of the maxillary complex, which if not remedied limits the potential use of the dental implant.
To overcome the deficiency of insufficient vertical bone mass of the maxillary complex, several surgical techniques have been developed to increase available bone mass for the placement of dental implants. These techniques augment the bone deficient region with a filler or regenerative material made of natural and/or artificial (synthetic) materials (collectively, ‘bone graft material’). Such material is placed on the roof of the maxillary structure under the subantral membrane so that it does not interfere with the function of the maxillary sinus. Collectively, these procedures are known within the dental profession as “sinus elevation procedures” with the goal of increasing the vertical height available for placement of dental implants. What makes these techniques unique from other techniques, such as distraction osteogenesis, is that the bone is increased within a body cavity, i.e., the maxillary sinus cavity.
Bone augmentation of the maxillary sinus requires careful bone removal and delicate dissection of the subantral membrane from the floor of the sinus. If the membrane is not properly dissected from the bone, bone augmentation may not occur, or may not be sufficient. Unintentional perforation of the subantral membrane may also lead to undesirable short and long-term consequences. If the perforation is large, for example, several millimeters in diameter, the surgeon must either abort the procedure or must use some means of removing or containing the bone graft material on the floor of the sinus to encourage new bone growth. Typically, a collagen membrane patch is used to repair the perforation and contain the bone graft material on the floor of the sinus. A lack of integrity of the membrane can also lead to the migration of bone graft materials leading to long-term chronic infections. Therefore, the maintenance of membrane integrity is of utmost importance during the elevation of the membrane to allow placement of bone graft materials with a goal of increasing bone mass in the maxilla.
A commonplace sinus elevation procedure requires a window into the maxillary sinus from a lateral and superior approach to the floor of the sinus. Great care must be taken during the entry to the sinus as it is critical not to perforate the subantral membrane that lines the sinus cavity. Most patients and dental surgeons acknowledge that entrance into the maxillary sinus utilizing a lateral window approach (also known as the Caldwell-Luc procedure) is an invasive procedure. This technique is fraught with many risks and complications because of the limitations of healing potential in the maxillary sinus. In spite of these risks many patients undergo this procedure because of the strong desire to replace missing maxillary teeth with dental implants.
An alternative procedure described by Dr. R. B. Summers approaches the maxillary sinus from the alveolar ridge utilizing solid cylindrical osteotomes. It is a more conservative approach and is less invasive. The technique vertically lifts the subantral membrane from the floor of the maxillary sinus via an infracture of the bony floor. The infracture can be performed using solid cylindrical osteotomes with specific diameters that are vertically advanced toward the maxillary sinus producing a mechanical lifting action on the membrane. Bone graft material is then placed into this space for bone augmentation. The bone graft materials are actually used to raise the subantral membrane. While this technique is safer than the lateral window approach, an overzealous use of an osteotome during the procedure can result in the perforation of the subantral membrane with disadvantages discussed above.
Thus, in prior art techniques, advancing a bone cutter through the maxillary bone with insufficient control or feedback may result in tearing or ripping of the subantral membrane. Overcoming these previous limitations in the technique of sinus elevation will reduce infection, bleeding, swelling, pain, suffering and failure when using dental implants in the maxillary sinus.